Can anyone recommend a secure online calendar that will allow me to store my data on the runbox servers, and that will sync with an android tablet, and possibly a Blackberry 10 device?

I'd like to move away from Google calendars, and be able to access my calendar on multiple devices. I'd like to be able to add events on one device, and have them show up on the synced calendar on the others without adding them multiple times.

I was hoping to have a calendar app (Acalendar+ looks good) installed on a phone and a seperate tablet, and be able to add an event on the phone, and have it show up on the calendar on the tablet, without having to enter it on the tablet's calendar seperately. It looks like CalDav should do it somehow.

Can you give me a rough idea how to add the calendar data onto the runbox server?

I was hoping to have a calendar app (Acalendar+ looks good) installed on a phone and a seperate tablet, and be able to add an event on the phone, and have it show up on the calendar on the tablet, without having to enter it on the tablet's calendar seperately. It looks like CalDav should do it somehow.

Can you give me a rough idea how to add the calendar data onto the runbox server?

If you have the same Google account on an Android 'phone and an Android Tablet, you only have to purchase one copy of CalDAV-Sync, and you may install it on both devices.

Once you have CalDAV-Sync installed on an Android device:

Add account = CalDAV
Server name = https://dav.runbox.com/
SSL = checked
Username
Password = create an app spec password in Runbox first
Select calendars to sync = There should be two there already: Home & Work - Select one or both to test.
Enter email address associated with this account = username@runbox.com

That's about it from the CalDAV-Sync side of things.

If you go into Google Calendar on your Android device, into settings, you should see the additional Runbox calendars there.

Adding new calendars into Runbox is more complicated, but if you can accomplish the above successfully, I can try to help.

I installed CalDav last night, as per your instructions. Then I had a look at my Blackberry, and realised that that had the option of adding CalDav calendar as standard.

I had a read up on the Runbox support, and managed to set up the Runbox calendar on the Runbox site, and I've now managed to link the tablet, and the Blackberry to the same calendar. I tried them out, and if I add events on one device, they appear on the other, and likewise if I delete them from one, they disappear on the other, which is exactly what I wanted.

Now I just have to figure out how to transfer the events on my Google to the Runbox one, and I can dump the google one.